Extraction of petroleum products and solvent therefor



Patented July 20, 1954 EXTRACTION OF PETROLEUM PRODUCTS AND SOLVENT THEREFOR Edgar W. Clarke, Laurel Springs, N. J assignor to The Atlantic Refining Company, Philadelphia, Pa., a corporation of Pennsylvania N Drawing.

Application March 20, 1952,

Serial No. 277,729

12 Claims.

This invention relates to an improved solvent for the refining of petroleum products and similar complex mixtures. More particularly, this invention relates to a new and novel solvent which has both high selectivity and high solvent power and comprises aniline, carbon disulfide and nitrobenzene.

dioxide mixed with benzol was a better solvent than sulfur dioxide alone and use of this mixed solvent was extended to the refining of heavy aromatic crude stocks in order to produce lubricating oils.

During the years 1925 to 1933, five additional solvent processes were commercially developed for the extraction of lubricating oil stocks. The

extraction solvents which have been widely employed on a commercial scale for the production 'of improved lubricating oils are: sulfur dioxidebenzol, Duo-sol, furfural, phenol, Chlorex, and nitrobenzene.

However, all six of these extraction processes suffer an inherent disadvantage in that they are highly inefficient. In order to obtain a raiflnate oil of the desired physical properties from aromatic crude stocks, it was heretofore necessary to operate the extraction apparatus in such a manner that a large proportion of the desirable material in the charge stock was lost in the extract phase.

The industrial need for an improved extraction solvent is shown by the fact that in the ten years following the actual development and use of the aforementioned six commercially employed processes for the extraction of lubricating oil stocks, more than 1000 United States patents were issued for new solvents or modified solvents. Without exception, all of these patents failed to achieve universal commercial acceptance for one basic reason-none of the suggested solvents possessed both of the two necessary characteristics of an ideal solvent for lubricating oil extraction. These two characteristics are high solvent power and high solvent selectivity.

High solvent power is desired in a solvent in order to minimize the ratio of solvent to charge stock. High solvent selectivity is desired so that the solvent will remove or selectively extract only the undesirable components of the charge stock and therefore prevent losses of large amounts of desirable components in the extract phase.

A few solvents, such as aniline, exhibited excellent selectivity but had very little solvent power. The necessary solvent charge stock ratio for extraction processes employing aniline would be so great that the process would be uneconomical. Industry preferred to continue using solvents of high solvent power and moderate selectivity, such as nitrobenzene or hot furfural. By the use of these solvents which have only a moderate selectivity in the extraction of aromatic crudes, from 10% to over of the valuable lubricating oil components of the charge stock were diverted along with the really undesirable materials into the extract layer. This loss of solvent oil was eventually considered as simply in inherent characteristic of extraction processes.

It is therefore an object of this invention to provide a solvent composition which possesses both high solvent power and high selectivity. It is a further object'of this invention to provide a solvent composition which minimizes loss of the desirable components of a charge stock to the extract phase.

The present invention is based upon the discovery that a solvent composition comprising aniline, nitrobenzene, and carbon disulfide is capable of fulfilling the aforementioned objects of obtaining a solvent having both high solvent power and high selectivity. The idea of extracting lubricating oil stocks with a mixture of nitrobenzene and aniline is not new in the patent literature. Several investigators have mentioned the possibility of combinations of solvent which included nitrobenzene and aniline. However, in no case in the patent literature, or elsewhere, was laboratory or pilot plant data submitted for demonstrating the feasibility of continuous operation of any extraction process using as a solvent mixtures of aniline and nitrobenzene. The reason is perfectly obviousaniline slowly reacts with nitrobenzene and the end product of this reaction is a sticky material somewhat resembling off -grade synthetic rubber. This highly undesirable product will contaminate the rafifinate and extract phases, cause troublesome recycle problems, plug various parts of the extraction apparatus, and in general will render an extraction unit highly impractical if not impossible to operate. It was found that conventional anti-oxidants or similar inhibitors could not entirely prevent this reaction between the nitrcbenzene and aniline, since such inhibitors were constantly either, (1) separated from the solvent during solvent stripping, (2) rendered ineffective by the heat accompanying the stripping operation, or (3) decomposed into products which discolored or otherwise contaminated the rafiinate phase.

According to this invention, it has been discovered that a solvent composition comprising aniline and nitrobenzene may be successfully used in an extraction process without encountering the aforementioned diificulties, if carbon disulfide is incorporated with the solvent composition. Such a solution was employed for 16 consecutive laboratory extractions, heated, refluxed, and stripped over a six months period. At the end of this time the solutions were no darker in color than a mixture of equal volumes of pure aniline and nitrobenzene which had been contacted for two minutes at room temperature. Solutions of pure aniline and nitrobenzene which were employed for repeated extractions ruined the quality of the rafiinate oils by turning them black.

The volume proportions of aniline to nitrobenzene can be varied between 1:9 and 9:1, depending upon the particular extraction conditions, but the aniline is ordinarily in smaller amounts, usually less than a 1:1 volume ratio, and preferably between a 1:9 and a 1:3 volume ratio. The amount of carbon disulfide necessary in order to inhibit the reaction between aniline and nitrobenzene is usually between 0.001 and 0.01 volume per volume of the aniline, although greater or smaller amounts may be employed in some instances.

The superiority and utility of the instant invention can be illustrated by the data set forth in Table I below which represent three-stage batch extractions of an oil solution of barium sulfonates to produce a superior motor oil detergent. In each case the charge stock entered thefirst stage and flowed countercurrently to the extraction solvent which entered the third stage. The raffinate layer was withdrawn from the third stage and the extract layer was withdrawn from the first stage.

TABLE I Three stage batch, countercurrent extractions of oil solution of barium sulfonate Solvent Composition 100% Nitrobenzene. Solvent/Charge Ratio, Vol. Percent 300. Extraction Temperature, F 41.

Charge Stock Raiiinate Extract Volume Percent Yie1d Percent Suliated Ash A. P. I. Gravity Refractive Index at (Single 8 (Single Solvent Composition Aniline. Solvent/Charge Ratio, Vol. Percen 300 Extraction Temperature, "F "I: 60.

Charge stock Rafiinate Extract Volume Percent Yield 100-. 20. Percent Sulfated Ash... 3.46. 3.47. A. P. I. Gravity 19.1. 17.3. Refractive Index at 1.47320 1.48442.

176 F. Color, ASTM (D- 8 (Single 8 (Single 6 (Double 451) dilution) dilution) dilution) 58.0%,ylitrobenzene. 4 .75 ni ine. Solvent Composition 025% Carbon 355mb e. Solvent/Charge Ratio, Vol. Percent 300. Extraction Temperature, F 55.

2:2? Rafilnate Extract Volume Percent Yield.. 70 30. Percent Suiiated Ash. 3.76 2.78. A. P. I. Gravity 19 21.5 17.6. Religgctive Index at 1 46920 1.48253.

17 F. Color, ASTM (D155- 8 (Single 4% (Single 5 (Double 451) dilution) dilution) dilution) The data in Table I show that nitrobenzene had too great a solvent power and no selectivity for the extraction of barium sulfonates. This was true even at {11 which was the temperature at which solid nitrobenzene settled out of the solution. By contrast, aniline had too little solvent power and in spite of excellent selectivity there was no appreciable improvement in the quality of the rafiinate over the charge stock.

In the extraction of barium sulfonate with the improved solvent of this invention, the sulfonate was concentrated in the raff nate together with the desirable higher viscosity index components of the oil solution. The direct measurement of the viscosity index of the sulfonate-free oil before and after the extraction was not feasible in either case, due to the difficulties in physically separating the solution into oil-free sulfonate and sulfonatefree oil fractions. However, it is a Well established experimental fact. that reduction in the undesirable lower viscosity index components of a sulfonate-free oil. solution by solvent extraction is always accompanied by a decrease in refractive index, increase in A. P. I. gravity, and decrease in ASTM color. Hence the improvement. in the viscosity index of the oil solution in the solventfree rafiinate was established from the decrease in refractive index, increase in A. P. I. gravity, and reduction in ASTM color, of the rafiinate compared with the corresponding untreated oil solution of barium sulionate charged to the extraction unit.

i no difference had occurred in the quality or composition ofthe oil in the raffinate as compared to the oil in the charge stock, an increase in concentration of the sulfonate in the rafiinate solution would have increased the refractive index, decreased the A. P. I. gravity, and increased the ASTM color of the oil solution of the detergent. Any decrease in the refractive index or color, or increase in the A. P. I. gravity of the sulfonatefree raffinate oil solution which accompanied an increase in the concentration of the detergent (as evidenced by ash content), could only have been explained by a reduction in the undesirable lower viscosity index components of the-oil solution.

As a further illustration of the utility of this invention, an East Texas deasphalted residuum was subjected. to. a twelve-stage solvent extraction 3 operation to compare the relative efiiciency of a solvent composition, A, comprising 98% phenol and 2% water, and a solvent composition, B, comprising 75% nitrobenzene, aniline, and 1% carbon disulfide based on the amount of The extraction with solvents A and B in the above table were carried out to produce a dewaxed rafiinate having a viscosity index of 85. It will be noted that by using solvent B a ten per cent greater raffinate yield was obtained. In

addition, the use of solvent B permitted a smaller solvent to charge ratio and a lower extraction temperature. It is thus seen that the solvent of this invention is superior to the phenol solvents which are currently used in many refining processes.

The utility of the solvent of this invention was further demonstrated by extracting a yellow microcrystalline wax charge stock which had an average molecular weight of 535 and having an average number of Cc rings per molecule of about 1.3. The raiiinate from this extractionwas a high molecular weight, refined, polycyclic, white naphthenic wax having an average molecular weight of 755 and an average number of C6 rings per molecule of about 2.1. This raffinate product was found to be an excellent additive for laminating waxes since due to its high molecular weight and high average number of rings per molecule, it possessed tensile strengthening properties. No other solvent or combination of solvents is known which would produce a high molecular weight, refined, polycyclic, naphthenic wax of this type.

Even when the above microcrystalline charge stock was vacuum distilled at a total pressure of one micron (which could not be commercially attained) the high temperatures required by distillation caused thermal decomposition to take place. Distillation concentrated the high molecular weight bottoms as a sticky brown residue, instead of producing a white wax of refined quality.

The improved solvent was also employed for the extraction of the residuum from a non-lube cracking crude. A ten per cent San Joaquin residuum was selected as typical of a low value stock which was a practically non-saleable product useful only for cracking or burning, and which could not be solvent extracted with any of the known prior art solvents. This residuum was treated with a nitrobenzene, aniline, carbon disulfide, solvent mixture to produce a raifinate which was suitable as a N o. 6 fuel oil, and an extract that consisted of a mixture of resin and naphthenic wax. By conventional solvent dewaxing the extract, a naphthenic wax was obtained which was a valuable additive for upgrading parafiin wax for specialty uses together With a resin having equally valuable uses as an additive.

The solvent of this invention in addition to being useful in separating wax, sulfonates, resins, and fractions of a particular viscosity index from hydrocarbon oils (illustrated by the above GX-r amples), may also be employed to refine other hydrocarbons or mineral oil fractions, such as cracked naphthas, gasolines, or kerosenes, whose boiling ranges are sufficiently different from the solvent to permit separation. Therefore, subject to the above limitations, the solvent of this invention may be utilized whenever it is desired to separate a lnldrocarbon oil into a plurality of fractions differing by viscosity, boiling range, gravity, color, viscosity-gravity constant, wax content, or the like.

The nitrobenzene, aniline, carbon disulfide composition of this invention may be used in a number of ways. For instance, when a multistage extraction is employed, the nitrobenzene may be introduced into one-stage of the unit and the aniline in another stage so that the aniline functions as an additive. The exact point of introduction of each of these materials will depend upon the particular type of extraction being carried out, as well as the apparatus and conditions which are utilized. The carbon disulfide may be incorporated with either the nitrobenzene or aniline or with both. The solvent of this invention may also be employed in conjunction with other solvents well-known in the art to effect improved separation or extraction in particular instances.

I claim:

l. A selective solvent comprising major amounts of nitrobenzene and aniline, and minor amounts of carbon disulfide not substantially in excess of that suificient to inhibit the reaction between the nitrobenzene'and aniline.

2. An extraction solvent comprising 10 volumes to volumes nitrobenzene, 90 volumes to 10 volumes of aniline, and 6.001 volume to 0.01 volume of carbon disulfide per volume of aniline.

3. A method of refining hydrocarbon oils which comprises contacting the oil with a solvent comprising a mixture of nitrobenzene, aniline, and minor amounts of carbon disulfide not substantially in excess of that sufficient to inhibit the reaction between the nitrobenzene and aniline to produce rainnate and extract phases, separating the phases from each other, and recovering the solvents therefrom.

4. The method of separating a hydrocarbon oil into fractions having different physical and chemical properties which comprises admixing said hydrocarbon oil with a solvent mixture comprising nitrobenzene, aniline, and minor amounts of carbon disulfide not substantially in excess of that sumcient to inhibit the reaction between the nitrobenzene and aniline to form an extract and raffinate phase, separating said phases, and removing the solvents therefrom.

5. The method of separating a hydrocarbon oil solution of sulfonates into fractions of greater and less concentration which comprises contacting said oil solution with a solvent mixture comprising nitrobenzene, aniline, and minor amounts of carbon disulfide not substantially in excess of that sufficient to inhibit the reaction between the nitrobenzene and aniline to form raninate and extract phases, separating said phases and removing the solvents therefrom.

6. A process of refining a hydrocarbon oil containing both high viscosity index hydrocarbons and low viscosity index hydrocarbons, comprising extracting the oil with a solvent mixture comprising nitrobenzene, aniline, and minor amounts of carbon disulfide not substantially in excess of that suificient to inhibit the reaction between the nitrobenzene and aniline to form a high. viscosity index hydrocarbon phase and a low viscosity index hydrocarbon phase, separating the phases and removing the solvents therefrom.

7. The method of dewaxing hydrocarbon oils which comprises contacting said oil with a solvent mixture comprising nitrobenzene, aniline, and minor amounts of carbon disulfide not substantially in excess of that sufficient to inhibit the reaction between the nitrobenzene and aniline to form rafiinate and extract phases, separating said phases and removing the solvents therefrom.

8. A method of refining hydrocarbon oils which comprises contacting the oil with a solvent comprising 10 volumes to 90 volumes nitrobenzene, 90 volumes to 10 volumes of aniline, and 0.001 volume to 0.01 volume of carbon disulfide per volume of aniline to produce rafiinate and extract phases, separating the phases from each other, and recovering the solvents therefrom.

9. The method of separating a hydrocarbon oil into fractions having different physical and chemical properties which comprises admixing said hydrocarbon oil with a solvent mixture comprising 10 volumes to 90 volumes nitrobenzene, 90 volumes to 10 volumes of aniline, and 0.001 volume to 0.01 volume of carbon disulfide per volume of aniline to produce raflinate and extract phases, separating said phases, and removing the solvents therefrom.

10. The method of separating a hydrocarbon oil solution of sulfonates into fractions of greater and. less concentration which comprises contacting said oil solution with a solvent mixture comprising 10 volumes to 90 volumes nitrobenzene, 90

volumes to 10 volumes of aniline, and 0.001 volume to 0.01 volume of carbon disulfide per volume of aniline to form raffinate and extract phases, separating said phases and removing the solvents therefrom.

11. A process of refining a hydrocarbon oil containing both high viscosity index hydrocarbone and low viscosity index hydrocarbons, comprising extracting the oil with a solvent miX- ture comprising 10 volumes to 90 volumes nitrobenzene, 90 volumes to 10 volumes of aniline, and 0.001 volume to 0.01 volume of carbon disulfide per volume of aniline to form a high viscosity index hydrocarbon phase and a low viscosity index hydrocarbon phase, separating the phases and removing the solvents therefrom.

12. The method of dewaxing hydrocarbon oils which comprises contacting said oil with a solvent mixture comprising 10 volumes to 90 volumes nitrobenzene, 90 volumes to 10 volumes of aniline, and 0.001 volume to 0.01 volume of carbon disulfide per volume of aniline to form rafiinate and extract phases, separating said phases and removing the solvents therefrom.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,017,432 Bahlke Oct. 15, 1935 2,129,616 Grote et a1 Sept. 6, 1938 2,141,361 Pilat et al Dec. 27, 1938 2,301,965 Mauro et al Nov. 17, 1942 

1. A SELECTIVE SOLVENT COMPRISING MAJOR AMOUNTS OF NITROBENZENE AND ANILINE, AND MINOR AMOUNTS OF CARBON DISULFIDE NOT SUBSTANTIALLY IN EXCESS OF THAT SUFFICIENT TO INHIBIT THE REACTION BETWEEN THE NITROBENZENE AND ANILINE.
 3. A METHOD OF REFINING HYDROCARBON OILS WHICH COMPRISES CONTACTING THE OIL WITH A SOLVENT COMPRISING A MIXTURE OF NITROBENZENE, ANILINE, AND MINOR AMOUNTS OF CARBON DISULFIDE NOT SUBSTANTIALLY IN EXCESS OF THAT SUFFICIENT TO INHIBIT THE REACTION BETWEEN THE NITROBENZENE AND ANILINE TO PRODUCE REFFINATE AND EXTRACT PHASES, SEPARATING THE PHASES FROM EACH OTHER, AND RECOVERING THE SOLVENTS THEREFROM. 